Sakuya is the only human living in the Scarlet Devil Mansion, yet she is also the head maid. Hieda no Akyuu theorises that she had been a vampire hunter before she began working in the mansion, after being defeated by Remilia Scarlet, she was given her current name and began working for the mansion, but such is yet to be confirmed.

Though she looks about sixteen like the other girls, Sakuya has the ability to slow, stop and possibly reverse time. She seems to have been serving Remilia for a long time and may be far older then she looks. Socially, she interacts mainly with the others in the Scarlet Devil Mansion.

Her talents are cooking, knife throwing and time manipulation. The latter two abilities characterize her appearances in-game, and led to frequent parodies in reference to Dio Brando of JoJo's Bizarre Adventure, who also controls time and throws knives. This reference goes so far as Sakuya using some of his poses in a game. She is often associated with dogs by other characters because she is serving as a demon's "faithful guard dog" even though she is a full blood human.

(Source: Wikipedia)